Grinding machine assemblies



UnitedStettes Patent GRINDING MACHINE ASSEMBLIES George Dewey Behlen, Cincinnati, Ohio, assignor to The United States Electrical Tool Co., Cincinnati, Ohio, a corporation of Ohio Filed Nov. 4, 1957, Ser. No. 694,298

4 Claims. (Cl. 51-1345) My invention relates specifically to hydraulic drives for grinding machines.

Grindingmachines are ordinarily equipped with high speed bonded grinding wheels or vitrified grinding wheels. A bonded grinding wheel may have a surface speed of 9500 surface feet per minute. A vitrified grinding wheel may have a speed of 5500 surface feet per minute.

As grinding wheels wear down in use, a 30 inch diameter wheel may wear down to 15 inch diameter; a 24 inch diameter wheel may wear down to 15 inch diameter and a 20 inch diameter wheel may wear down to 13 inch diameter. If the rate per minute rotation of the shaft on which a grinding wheel is mounted remains constant, as the peripheral surface of the wheel is worn down the surface feet per minute is reduced so that work planning in large quantity production plants becomes erratic.

There is a point reached in the grinding of a metal part where if the surface feet per minute is reduced enough the grinding process becomes the metal grinding down the grinding wheel instead of the grinding wheel grinding 01f the work. It is for this reason that the maintenance of the surface feet of travel per minute of the peripheral grinding surface of the wheel becomes so very important.

With the advent of more and more accurate planning of machine shop operation, it becomes important as far as grinding wheels-are concerned that the surface feet per minute speed of grinders be maintained at a substantially constant speed. This I accomplish by an automatically controlled combination of elements which increases the rate of rotation of the grinding wheel shaft as the grinding surface is worn down so that substantially constant surface feet per minute speed of the peripheral grinding surface is maintained.

I accomplish my objective by an arrangement of driving elements consisting of a constant speed electric motor, an hydraulic pump actuated by the electric motor and delivering a constant flow of fluid, a variable displacement piston type hydraulic motor and a flexible coupling through which rotation is imparted to the grinding wheel shaft. As an additional safety factor I may incorporate in the assembly a flow control and overload relief valve between the hydraulic pump and the variable displacement niston type hydraulic motor.

The individual mechanisms of which my combination is made up are for the most part old and well known in the art. Thus any desired type of constant speed elec tric motor may be employed. Thus I find an electric motor developing the horse power at 1200 r.p.m. adequate for my combination.

The shaft of the motor is connected by a flexible coupling with a constant delivery vane type pump. The discharge from this constant delivery vane type pump is through a proportional type oil filter.

The constant flow of oil passes through a flow control and overload relief valve. An integral relief valve is independently adjustable and serves to limit the maximum operating pressure.

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The oil under pressure passes to a variable displacement piston type hydraulic motor. This motor provides means for the conversion of hydraulic power to reversible variable speed adjustable torque rotary mechanical power.

The rotary mechanical power is transmitted to the drive shaft of a grinding wheel and my invention relates to a control for the hydraulic motor so that the speed of rotation of the grinder drive shaft may be regulated to produce a substantially constant surface feet per minute speed of the grinding surface of the grinder wheel.

The foregoing general objectives I accomplish by that combination of elements of which I have illustrated a preferred embodiment.

In the drawings:

Figure l is a plan view of an assembly incorporating my invention.

Figure 2 is a slightly enlarged side elevation of the operating parts showing my control for the surface speed of the grinder wheel.

Figure 3 is a sectional view taken along the lines 3-3 of Figure 2.

Figure 4 is a sectional view taken along the line'44 of Figure l.

Figure 5 is a perspective view of the cam surface fork, which is part of the mechanism varying the speed of rotation of the hydraulic motor.

Figure 6 is a detail perspective view of the mechanism which the cam surfaced fork shown in Figure 5 engages.

The electric motor 1 is provided with electrical contacts from a suitable source of electric power and the motor shaft 2 is connected with a flexible coupling 3 to the shaft 4 of a constant delivery vane ty-pe pump 5 which has an intake 6 from a suitable reservoir and delivers a constant flow of oil under pressure through the discharge pipe 7.

A proportional type filter 7a is the first mechanism in the pipe from the oil pump and the filter is connected by a pipe 8 to the flow control and overload relief valve 9. Whilethis overload relief valve forms no essential part of my combination, I have found its incorporation in a preferred system desirable. V i

The relief valve 9 may be' used to accurately regulate the flow of oil to the hydraulic motor. An integral relief valve is independently adjustable and serves to limit the maximum operating pressure. With this method of flow control the variable speed hydraulic motor is required to develop only the minimum amount of pressure necessary to maintain operating speed. Further more smooth and uniform operation, regardless of the change in work load may be maintained.

The discharge from the flow control and overload relief valve 9 passes through the pipe 10 to the variable displacement piston type hydraulic motor generally indicated at 11.

Since the variable displacement piston type hydraulic motor forms no part of my inveniton, for purposes of understanding its operation I may state that such a mechanism is accurately described in the Harrington and Robinson US. Patent No. 2,472,477.

The hydraulic motor 11 has a control shaft 12, the movement of which lengthwise changes the position of the piston within the motor and so changes the rate of rotation of the shaft 13 driven by the motor 11. The shaft 13 passes through a bearing housing 14 and causes the rotation of the shaft 15 on which the grinding wheel 16 is mounted.

A spark guard plate 17 is retained in slides 18 in the assembly housing. This spark guard plate is normally adjusted to remain A1, inch from the peripheral grinding surface of the grinding wheel. A clamp bolt 19 is held in position clamping the spark guard plate by means of a hand wheel 20. When the hand wheel is loosened the plate,17 may be set intadesiredpositionin thegslides 1,8.

The clamp plate has a bolt 21 which extends through a slot 22 in the long leg or arm 23 of a lever pivoted at 24. The short; leg or arm 25 of .thelever carries ,a forked member 26 i having cami faces 27.

The speed control shaft.1 2 of the motor 11 has a. cam faced .washer 28 held in position by a nut 29 threaded on the outer, end of the shaft 12 (see Figure 4). A coil spring 30 within thehousing tends to move the speed adjustment shaft,12, to the right as indicated in Figure 4. However, it is the cam faces of the forked member 26 hearing against the washer .28 which controls the position of the shaft 12.

As the operator of the grinder moves the spark guard plate 17 down to maintain the quarter inch clearance from the grinding wheel, the long leg 23 of the lever moves down and the short leg 25 moves up about the pivot 24. :This actionelevates the fork 26 and pulls the shaft 12 outwardly, thereby speeding up the motor 11 to increase the rate of rotation of the shaft carrying the grinding wheel. Thus as the spark guard plate is adjusted to maintain the A inch clearance from the grinding wheel the peripheral surface speed ofthe grinding wheel is maintained.

The combination shown illustrates amanual control but it is within the scope of my invention to control the position of the spark guard plate by a free running roller which actually contacts the periphery of the grinding wheel and is connected by suitable mechanical parts to the, plate 17, which in this instance would be freely movable in the slides 18.

Thus when in the claims which follow I refer to a control for the adjustment of the shaft 12, it will be understood that reference is made to a manually adjustable control or one automatically determined by the position of the grinding surface of the grinding wheel.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In combination with a variable displacement piston type hydraulic motor suitably connected with the drive shaft of a grinding wheel, said motor having a mechanical element for controlling the speed of operation of said motor, a grinding wheel mounted-on said drive shaft, a spark guard plate associated with said grinding wheel and means connecting said guard plate and said mechanical element to regulate the rate of operation of said motor ,d pendentoathe wear ofth p r p y s i r ng wheel and the relative position of said guard plate with respect to the periphery of said grinding wheel.

2. In combination with a variable displacement piston type hydraulic motor suitably connected with the drive shaft of a grinding wheel, said motor having a mechanical element for controlling the speed of operation of said motor, agrinding wheel mounted on said drive shaft, a spark guard plate associated with said grinding wheel and means connecting said guard plate and said mechanical element to regulate the rate of operation of said motor dependent on the wear of the periphery of said grinding wheel andthe relative position of said guard plate with respect to the periphery of said grinding wheel, said means comprising a lever having one arm connected to said spark guard plate and the other arm connected to said mechanical element.

3. In combination with a hydraulic motor connected to the drive shaft of a grinding wheel, means manually adjustable to compensate for the wear of the peripheral surface of said grinding wheel for controlling the speed of operation of said hydraulic motor to maintain the surface feet per minute speed of said grinding wheel, said means comprising a spark guard plate associated with said grinding wheel, and said means further comprising a pivoted lever having one arm connected with said spark guard plate and the otherarm connected with said hydraulic motor.

4. In combination with a grinding wheel mounted on a, shaft and having a variable speed hydraulic motor for driving said grinding wheel shaft manually adjustable means adapted to compensate for the degree of wear of said grinding wheel for regulating the speed of said hydraulic motor, said means comprising a spark guard plate associated with said grinding wheel and maintained at a constant distance from the working surface of the grinding wheel, said hydraulic motor having a mechanical elementfor regulatingits speed and said spark guard plate connected with a lever to said mechanical element.

References Cited in the file of this patent UNITED STATES PATENTS hi -a 

